Further Rise In Temperature Research Articles

Shrinkage and Creep of Concrete Containing 50% Lignite Fly Ash at High Temperatures

Abstract This paper investigates the influence of high temperature on the shrinkage and creep of unsealed and sealed concrete containing 50% Saskatchewan lignite fly ash and 50% Type I portland cement. Concrete was tested at six different temperatures between 70 and 450°F (21 and 232°C) and under three stress levels of 750, 1200, and 1500 psi (5.2, 8.3, and 10.3 MPa). The tests were made on 3 by 9-in. (75 by 225mm) concrete cylinders, and shrinkage and creep were measured for a maximum period of 112 days. It was found that the shape of the shrinkage and the creep time curves were similar at both normal and elevated temperatures. Test results also showed that shrinkage and creep of unsealed specimens decreased with a rise in temperature from 70 to 350°F (21 to 177°C) and then increased with a further rise in temperature. Creep of sealed specimens was found to increase with a rise in temperature from 70 to 160°F (21 to 71°C) and then to decrease with a further rise in temperature. Shrinkage and creep of unsealed specimens were nearly the same as those of plain concrete at the age of 112 days and at temperatures of 70 to 450°F (21 to 232°C).

Thermal treatment of sepiolite— And palygorskite— Stearic acid associations

The interactions between stearic acid and the clay minerals sepiolite and palygorskite and the thermal behaviour of the organo-clay associations were investigated by DTA, TGA and IR spectroscopy. The molten acid was adsorbed by the clay minerals, penetrating into the channels and exchanging zeolitic water. Inside the channels the acid was hydrated. When the organo-clay associations were ground, the acid dissociated to form stearate anions, due to interaction of the protons with newly exposed basic surface sites. Alkali halide disks of the organo-clay complexes were heated in stages up to 450°C and their IR spectra were recorded. Most of the adsorbed acid was liberated from the clay below 190°C. With NaCl disks, loss of organic material continued with a further rise in temperature, but with KCl and CsCl disks, increases in temperature led to decomposition of the acid, leaving a hydrocarbon residue. The thermal stability of the stearic acid—palygorskite association is lower than that of the sepiolite.

Field-effect studies on p-type CuInTe2 metal-insulator-semiconductor structures

Field effect studies on metal-insulator-semiconductor structures of p-CuInTe2 thin films grown on mica are made in the temperature range 77–295 K. An increase in carrier density and a decrease in the mobility is observed on the application of a negative gate field. The effect of a positive gate field is the opposite. The Hall coefficient is found to remain practically constant at a lower temperature range (77–180 K) and then decreases with a further rise of temperature. The study of the effective field effect mobility μFE reveals that the surface states charge scattering mechanism dominates the scattering process.

Thermal treatment of silica aerosil 200: Interrelated surface areas and heats of immersion in cyclohexane

Silica Aerosil 200 was thermally dehydrated at different temperatures in the range 20–1000 °C. The effects of thermal treatment on water loss and content, specific surface areas (as measured by cyclohexane vapour adsorption) and heats of immersion in liquid cyclohexane are presented and discussed. Brunauer-Emmett-Teller (BET) surface areas and the reciprocal of the average pore radius vary similarly when they are presented graphically as functions of the pretreatment temperature. The integral heat of immersion increases up to 300 °C and then decreases with a further rise in temperature to 1000 °C. This early increase in the integral heat of immersion (to 300 °C) is interpreted in terms of the removal of physisorbed water and an increase in cyclohexane areas in the range 110–380 °C. The heat of immersion calculated on the basis of unit area also has a maximum value at 300 °C and then decreases with a further rise in temperature. The measurable pore narrowing noted in the temperature range 110–380 °C explains qualitatively the early increase in the heat of immersion. The lyophobic surface fraction was calculated from the difference between the nitrogen and the methanol areas, or from cyclohexane areas, divided by the nitrogen BET surface area. As indicated from the present investigation, the lyophobic fraction calculated from the difference between the nitrogen and the methanol areas appeared to be a reliable measure of hydrophobic surfaces. This was revealed in more consistent changes with the average pore radius when the two parameters were represented graphically as functions of the pretreatment temperature.

Effect of Temperature on Starch Degradation in <italic>Chlorella vulgaris</italic> 11h Cells

Analysis of products formed in Chlorella vulgaris l l h cells during photosynthesis in air containing 3,000 ppm CC>2 at various temperatures revealed that the level of Cstarch was maximum around 20—24°C and decreased with further rise in temperature until 40°C, while C-sucrose greatly increased at temperatures above about 28°C. Elevating the temperature from 20 to 38°C during photosynthetic CO2 fixation resulted in a remarkable decrease in C in starch and a concomitant increase in C in sucrose. This conversion of starch to sucrose when shifting the temperature from 20 to 38°C proceeded even in the dark. Hydrolysis of sucrose by /?-fructosidase showed that, irrespective of the experimental conditions, the radioactivities in sucrose were equally distributed between glucose and fructose. The enhancement of starch degradation with temperature rise was more remarkable than that of the activity of ribulose bisphosphate carboxylase from the same cells. When Chlorella cells which had been preloaded with C-starch after photosynthesis for 30 min at 20°C were incubated in the dark for an additional 30 min at 20°C, C-starch was degraded by only about 4%. However, the values after 30-min dark incubation at 28, 32, 36 and 40°C were increased by about 10, 19, 36 and 50%, respectively. During the temperature-dependent conversion of starch to sucrose, no significant amount of radioactivity accumulated in free glucose and maltose.

Rheology of Plastisols of Poly(Vinyl Chloride)

Abstract The viscosity of PVC plastisols is seen to be affected by numerous variables. Increase in concentration of the resin causes the viscosity to rise, with the increase being more abrupt at the higher concentrations. Deviation from Newtonian behavior also increases with concentration. Decrease in the size of particles results in an increase in viscosity, the effect being more pronounced at low shear rates. Broadening the distribution of particle sizes results in a decrease in viscosity. Porous particles yield plastisols with higher viscosity as compared to nonporous compact particles. The type of plasticizer also affects the viscosity. A plasticizer which is a better solvent for PVC (low value of polymer-solvent interaction parameter, χ) results in a higher viscosity due to an increase in the amount of dissolved polymer. Additives such as alcohols and soaps affect the viscosity in an, as yet, unknown way. Fillers, heat stabilizers, and pigments also increase the viscosity. With increasing temperature, the viscosity first decreases, passes through a minimum and then increases until gelation. With further rise in temperature the viscosity again decreases and then levels out before degradation occurs. In future work, particular emphasis needs to be given to the understanding of the basic mechanism involved in the effect of additives on the flow behavior. Systematic experiments with a range of well-defined particle sizes and over a wide range of shear rates are also needed. A better understanding of the factors affecting the behavior of plastisols will go a long way in changing the art of plastisol formulation to a science.

Melting behavior of syndiotacticity‐rich poly(vinyl alcohol)‐water gel

AbstractThe melting temperatures of a syndiotacticity‐rich poly(vinyl alcohol)‐water gel were measured for concentrations below 70g.dm‐3. In the gel chilled at a temperature below about 15°C the melting point first decreased monotonously then sharply in a jump and again monotonously with decreasing concentration, whereas in the gel chilled above 20°C the melting point decreased monotonously through‐out. The change of the shear modulus of a gel chilled at 0°C with the rise of temperature from 0°C to the melting point was also measured. Initially the shear modulus decreased, then increased to a maximum value, and at last decreased towards the melting temperature, whereas a gel chilled at 40°C kept an almost constant value during heating from 40°C up to a high temperature and then decreased with further rise of temperature. The turbidity of dilute solutions chilled at 0°C passed a minimum and maximum with the rise of temperature in accord with the minimum and maximum of the shear modulus. It is thus concluded that in the gel chilled at temperatures below 15°C the junctions grow to some extent with the rise of temperature.

Blood Group Determination of Severely Charred Bodies—The Effects of Heating on the Blood Group Activity of A, B, AB and O(H) Active Glycolipids and A and B active Glycoproteins

Partially purified preparations of A, B, AB and O(H) active glycolipids and A and B active glycoproteins were heated and their group activities were examined. The A, B and O(H) glycolipids began to decrease in activity when heated above 120–130°C for 60 minutes ; the AB glycolipids, when heated above 100°C for 60 minutes ; the A and B glycoproteins, when heated at 130°C for 60 minutes. With further rise of temperature the activity of the preparations gradually decreased and the pattern of activity change was generally the same in all blood-group substances studied. The activities of A, B and O(H) glycolipids and of A and B glycoproteins disappeared completely when they were heated at 200°C for 5 minutes ; A and B activities of AB glycolipid at 180°C for 5 minutes.

Earth's heat budget

In several places recently (in particular 'The energy crunch', BBC TV, 26 June 1973) I have heard reference to the danger of permanent climatic change caused by the injection of large amounts of heat by man into the atmosphere and oceans. One simple argument runs like this: if the temperature rises sufficiently to cause melting of the white polar ice, its change in colour to ocean grey would result in a greater absorption of radiant energy from the sun, and hence a further rise in temperature.

Change in physicomechanical properties during aging of martensite-aging steels

1. The change in the lattice constant and resistivity of ferronickel and chromium — nickel martensite showed that diffusion of the alloying elements occurs over the temperature range 300–450 °C. The relative amount of alloying elements that diffuses out of the α-solid solution is substantially greater in ferronickel than chromium — nickel steels. 2. We established that there is a relationship between the lattice constant or resistivity and the hardening during aging: the larger the decrease in the lattice constant or resistivity, the greater is the hardness of the martensite. 3. The austenite formed during heating (at t = 550–650 °C) is paramagnetic and stable with respect to the γ→α transition. A further rise in temperature leads to destabilization of the austenite and causes it to be converted to martensite. The temperature at which stable austenite is formed and the destabilization temperature depend on the chemical composition of the base and the alloying-element content.

Respiratory response to temperature and temperature tolerance of some intertidal gastropods

On raising the temperature of Thais lapillus, Littorina littorea, L. littoralis, and L. saxatilis in air and when submerged, the oxygen uptake in air is consistently higher than in water up to the temperature at which heat death occurs. With a further rise in temperature after the snail has entered heat coma two distinct respiratory patterns emerge, namely, in submerged snails the respiratory rate falls until the temperature at which death ensues, whereas in snails kept in air the respiratory rate shows an initial rise followed by a fall prior to thermal death. The reasons for these two respiratory patterns are discussed. The temperatures at which snails enter heat coma are up to 10 °C lower than those which are lethal to the species so that heat coma is considered to be a potential zonation controller. Snails on entering heat coma have the foot relaxed and consequently are liable to desiccation of the mantle cavity which in air may prove to be lethal, whereas in water, snails which enter heat coma are not exposed to the hazard of desiccation. The coma temperatures of snails in air are a few degrees higher than in water, thus giving an additional safeguard against the dangers of desiccation. The temperature tolerance of Thais and Littorina spp. varies with geographical distribution. Heat coma and lethal temperatures of snails from Cardigan Bay are slightly higher when compared with snails from the Firth of Forth than would be expected if acclimation to the temperature of the environment were the only factor involved.

ADSORPTION OF CYCLOHEXANE AND BENZENE ON MIXED HYDROXIDES AND OXIDES OF MAGNESIUM AND ALUMINIUM

Seven mixed hydroxides of magnesium and aluminium were prepared, and phase and structural changes accompanying their dehydration were investigated by differential thermal analysis, thermogravimetric analysis, and X-ray diffraction techniques. The differential thermal analysis curves possess 2 peaks corresponding to those of parent hydroxides together with a new peak, and the thermogravimetric analysis curves show slight inflections. X-ray diffraction patterns of the mixed hydroxides possess the characteristic lines of the parent hydroxides together with three to five new intense lines which might indicate the formation of a double hydroxide. When the mixed hydroxides are progressively heated they give rise to products possessing patterns which first become diffuse and ultimately pass mainly into the spinel pattern.Adsorption isotherms of cyclohexane and benzene were measured on the mixed hydroxides and their dehydration products. Specific surface areas calculated by the application of the Brunauer, Emmett, Teller (B.E.T.) equation are in general in good agreement for the two adsorbates. The surface area increases with rise of dehydration temperature to a maximum at 500–600 °C and then decreases with further rise in temperature. This behavior is common to crystalline oxide systems and may be ascribed to the intermingling of decomposition, re-crystallization, and sintering processes. Variations in the molecular ratio of the mixed oxides (as much as 20-fold), and in the method of preparation, do not much alter the surface area.

ON THE LIFE-HISTORY OF RHIZOSTOME MEDUSAE. III. ON THE EFFECTS OF TEMPERATURE ON THE STROBILATION OF MASTIGIAS PAPUA

1. In the habitat, the first appearance of the ephyrae coincides with the sea water temperature of about 22° C.2. In the laboratory, the minimum effective range of temperature for induction of strobilation by giving zooxanthellae is found to be 20-22° C.3. Individuals with zooxanthellae, which have once failed to react by strobilation by 20-22° C., can no longer be induced for strobilation by a further rise of temperature.4. These individuals do react if they are cooled to 20° C. for about a month and then exposed to the higher temperature.

The dehydrogenation of cyclohexane vapor on silica-supported nickel catalysts

The dehydrogenation of cyclohexane vapor has been studied over nickel-on-silica catalysts in a flow system from 100 ° to 260 ° at atmospheric pressure. The fraction of cyclohexane converted to benzene ( C) was extremely low (about 0.01) between 100 ° and 180 °, while at 235 °, C increased to a maximum value around 0.25 and then rapidly decreased with further rise in temperature. In the range 150–220 °, the apparent activation energy was 30 ± 2 kcal/mole and the reaction rate dependence was zero order with respect to benzene, and first order with respect to cyclohexane and to the inverse of the hydrogen concentration. It is suggested that the slowest step in the reaction involves the initial formation, from adsorbed cyclohexane, of adsorbed cyclohexene and hydrogen. The results are contrasted and compared with earlier findings on benzene hydrogenation.

Changes in the Physical Properties of a Kaolinite Clay on Heating and their Structural Implications

The effect of heat on structural changes in kaolinite was studied by measuring density, loss in weight, linear shrinkage and moisture absorption of a 95% kaolinite clay heated to different temperatures. The results show that metakaoline is formed around 500°C, and it partially retains the structure of kaolinite. With further rise in temperature, the semblance of crystallinity is lost gradually and a new crystalline phase appears at about 850°C, as envisaged by Brindley and Nakahira.

Permanganate–oxalic acid as a redox initiator in aqueous media. Part II. Kinetics and degree of polymerization

AbstractThe rate of polymerization of aqueous methyl methacrylate under nitrogen at 32°C. is proportional to the first power of catalyst (MnO4−) concentration (0.633 to 15.83 × 10−5 mole/l.) at fixed concentrations of the activator (0.8 × 10−2 mole/l.) and monomer (6.204 × 10−2 mole/l.), independent of activator concentration over a wide range (0.50 to 0.0625 × 10−2 mole/l.), and proportional to the first power of monomer concentration within the range (0.94 to 7.52 × 10−2 mole/l.) at fixed concentrations of the catalyst (3.16 × 10−6 mole/l.) and the activator (0.8 × 10−2 mole/l.). The initial rate of polymerization attains a maximum value at 45°C., but falls with further rise in temperature. The rate of polymerisation is depressed by agitation after initiation, salts and organic solvents, and is accelerated by MnSO4 and complexing agent like NaF (only at low monomer concentration), and in presence of peptizers like sodium cetyl sulfate or cetyltrimethylammonium bromide. The separating phase in the absence of peptizers is a course coagulum, and possibly a steady state with respect to radicals is not attained at high catalyst concentration. Injection of catalyst late in a run increases both the rate of polymerization and yield in unpeptized systems and does the reverse in peptized systems. The molecular weight of the polymers increases in the course of a run and is also affected by change of catalyst concentration but not by activator concentration in the range where the rate of polymerization is independent of activator concentration.

Experimentelle Gesteinsmetamorphose—IV: Bildung anatektischer Schmelzen aus metamorphisierten Grauwacken

Experimental high-grade metamorphism and anatexis of different greywackes has been studied under 2000 atm H 2O-pressure. The high-grade metamorphic mineral assemblage is that of biotitecordierite-plagioclase-alkalifeldspar-quartz-gneisses, with in some cases sillimanite. Quantitatively, the mineral content differs (Table 3) due to the different chemical compositions of the metamorphosed greywackes. If the positions of the points in the ACF-diagram are corrected for the amount of brotite formed, then they give the right ratios of the quantities of the other observed minerals. For most of the investigated rocks an anatectic melt begins to form at 685°C, for others this temperature is higher, up to 725°C. As with metamorphosed clays, the first melt to be formed is an aplitic alkalifeldspar-quartz melt. But with small rise in temperature plagioclase is fractionally dissolved in the melt, together with a certain amount of biotite, cordierite and sillimanite. The composition of the melt changes quickly with rise in temperature from aplitic over granitic to granodioritic and in most cases to tonalitic. A tonalitic or sometimes a granodioritic composition is a final stage in the anatectic process of previous greywackes, because further rise in temperature scarcely changes the composition of the melts. The cotectic formation of tonalitic anateotic melts have been observed which have dissolved more quartz than would be supposed. The amount of melt increases quickly with rising temperature, but at about 780°C a maximum is reached. In most cases over 70 up to 96 per cent of the metamorphosed greywackes have been liquified; if the metamorphite contained especially high quantities of quartz and/or An-rich plagioclase then the amount of melt is smaller, but nevertheless it still comprises two-thirds of the anatectic rock complex. If separated from the crystalline remainder it can intrude and form tonalites or granodiorites, respectively. If not separated far from the place of formation it may represent the “granitoid” portion of migmatites. Results are given for the solidus-liquidus relations of plagioclases in complex anatectic systems; these are compared with those in the system Ab-An-H 2O.

The thermal conductivity of heavy water between 75° and 260° c at pressures up to 300 atm

The thermal conductivity of heavy water having an isotopic purity of 99-85 per cent was measured with a vertical coaxial cylinder apparatus at pressures between 24 and 294 atm in the temperature range 75° to 260°C. The pressure range of the experiments included the critical pressure (218 atm). Identical with the trend exhibited by water, the thermal conductivity of heavy water was found to increase with rising temperature to a shallow maximum near 110°C and to fall with a further rise in temperature. The influence of pressure on thermal conductivity was small, and at 75°C amounted to an increase of 0.77 per cent for a pressure rise from 1 to 100 atm. This is similar to the values reported for natural water by previous investigators [9, 11]. In comparison with natural water, the thermal conductivity of heavy water, in the range investigated, was always lower. According to these tests the ratio k H 2O / k D 2O increased almost linearly from 1·045 at 75°C to a value of 1·34 at 260°C. No measurements of the thermal conductivity of heavy water have previously been reported at temperatures above 82°C. Below this temperature the present data are in good agreement with earlier work.

Zone of Negative Temperature Coefficient in Hydrocarbon Oxidation

THE occurrence of a zone of negative temperature coefficient is a feature almost unique to hydrocarbon oxidation. It is most intriguing how the rate and extent of reaction, which at first increase rapidly with temperature and give rise to cool flames, begin to fall with further rise in temperature. Although, justifiably, there has been a great deal of speculation about the factors responsible for this zone, very little experimental work seems to have been done to explore it.

Factors affecting the production of chromosome aberrations by chemicals.

In the present paper, the results of a study on the influence of temperature, hydrogen ion concentration, and oxygen tension on the production of chromosome aberrations in Vicia root tips by maleic hydrazide (MH), di-(2, 3-epoxypropyl)ether (DEPE), and 8-ethoxycaffeine (EOC), are described. Variations in the hydrogen ion concentration of the treatment solutions did not significantly influence the effect of EOC and DEPE. In contrast, the MH effect was considerably diminished by raising the pH from 4.7 to 7.3. A marked increase in the frequencies of aberrations produced by DEPE and MH was obtained by raising the temperature from 3 degrees to 25 degrees C. The effect of EOC increased with rising temperature up to 12 degrees C. With a further rise in temperature the effect of EOC decreased, so that at 25 degrees C. it was of about the same magnitude as at 3 degrees C. The effect of EOC was completely inhibited, and that of MH partly so, when during the treatment (1) oxygen was excluded from the solution, (2) respiration was inhibited by azide or cyanide, or (3) phosphorylation was uncoupled from respiration by 2, 4-dinitrophenol (DNP). Pretreatments with DNP had a similar effect, but posttreatments did not influence the frequencies of aberrations. The effect of DEPE was unchanged by anoxia. Pre- or posttreatments with DNP did not change the total number of aberrations produced by DEPE, but the appearance of the effect was considerably delayed. The results are discussed.